Vitamin C is water-soluble and is not produced by the body itself; you get it from food or a supplement. Vitamin C contributes to the normal function of the immune system and to the protection of cells from oxidative stress.

How much vitamin C?

The reference intake (RI) for vitamin C is 80 mg a day. With vegetables and fruit you can usually reach that easily. Vitamin C also contributes to maintaining the normal function of the immune system during and after intense physical exercise; the beneficial effect is obtained with a daily intake of 200 mg in addition to the recommended daily intake. High doses can cause digestive discomfort in some people; follow the recommended daily dose on the label.

Which form?

Ascorbic acid is the most common form. Buffered forms (such as sodium ascorbate or Ester-C) are less acidic and some people with a sensitive stomach find them more comfortable. Plant-based vitamin C complexes, for example from acerola, contain other plant compounds besides vitamin C.

Zinc

Zinc is a mineral involved in hundreds of enzymatic reactions. Zinc contributes to the normal function of the immune system and to the protection of cells from oxidative stress.

How much zinc?

The reference intake (RI) for zinc is 10 mg a day. Depending on the amount of phytate in the diet, EFSA recommends about 7.5-12.7 mg a day for women and 9.4-16.3 mg for men. EFSA sets a tolerable upper level of 25 mg of zinc a day for adults, from all sources combined. Long-term high doses can disturb copper status. Always follow the recommended daily dose on the label.

Which form?

Commonly used forms are zinc bisglycinate, zinc citrate, zinc gluconate and zinc oxide. They differ in zinc content per gram and in price; the label shows how much zinc a product provides per daily dose.

Vitamin D, vitamin C and zinc each contribute to the normal function of the immune system. That is why they are often used together, for example in a multivitamin or as separate products.

What to look out for

• Vitamin D: follow the Dutch Health Council's advice for your age and situation and stay below the tolerable upper level of 100 micrograms a day.
• Vitamin C: the reference intake is 80 mg a day; follow the recommended daily dose on the label.
• Zinc: stay below the tolerable upper level of 25 mg a day, from all sources combined.
• Add it up: if you use a multivitamin and separate supplements, add up the total intake per nutrient.

Vitamin D, vitamin C and zinc are a logical trio: for all three, the EU has established that they contribute to the normal function of the immune system. A varied diet, enough sleep and exercise remain the foundation.

Disclaimer: This article is for information only and does not replace medical advice. A food supplement is not a substitute for a varied, balanced diet and a healthy lifestyle. If in doubt or if you take medication, consult a doctor or pharmacist. Do not exceed the recommended daily dose. Keep out of the reach of young children.